In recent years, top executives from U.S. technology giants such as Google, Microsoft and Intel routinely filed into a secured room deep inside the bowels of the National Security Agency’s headquarters in Fort Meade, Md.

During the visits, which continue today, the NSA and other U.S. government agencies provide classified, “top secret” intelligence about existing and potential cyber threats to company systems from foreign government attackers, such as China, Russia and Iran. This account is based on interviews with six people who have attended the meetings and others who have been briefed on the meetings by participants, all of whom requested anonymity because the discussions are supposed to be confidential.

At the meetings, officials from the agencies share information about threats they’ve discovered in order to help the companies defend themselves, the participants say. Both the agencies and companies share information about specific ways they have been attacked and compromised by hackers. In addition, executives have answered questions about how they would assist the government in the event of a major cyber war, these people say.

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An October meeting, for instance, began with an hour-long “threat brief” by the NSA and FBI. That was followed by an hour-long “discussion of current events” by the NSA, according to the website. The agenda for a September meeting says the participants planned to “refine” a document discussing “countermeasures” for cyber attacks known as “distributed denial of service.”

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